1. Field of the Invention
The present invention relates to a method of processing telephone signals.
2. Description of the Related Art
Hearing-impaired listeners who can hear sounds with the help of hearing aid devices often have difficulty hearing high-frequency sounds. Listeners with slight hearing impairment cannot hear sounds above 6,000 Hz, and those with severe hearing impairment cannot hear sounds above 2,000 Hz. For example, listeners with severe hearing impairment cannot hear sounds above 4,000 Hz even when the sounds are amplified to several times their original volume. Since consonant sounds are often above 4,000 Hz, the basic approach of hearing aid devices is to lower the frequency of the sound and to amplify it. In addition, hearing-impaired listeners can set some adjustable parameters according to their needs. The adjustable parameters are usually related to the frequency and the amplification of sounds to facilitate the processing of the sounds by the sound-processing program (software or firmware) inside the hearing aid devices.
When a hearing-impaired listener speaks with other people face to face, common hearing aid devices are sufficient, since the devices lower or remove high-frequency sounds so that the hearing-impaired listener can hear the original high-frequency sounds. However, when the hearing-impaired listener speaks to others on a telephone, problems may arise because the phone first removes the high-frequency sounds before transmission. For example, the traditional telephone first removes frequencies above 4,000 Hz before transmission. Therefore, no sounds above 4,000 Hz are sent through telephones, and hearing-impaired listeners cannot easily identify the correct sounds on telephones as long as one side uses a traditional landline (or even 2G and 3G phones), particularly in the case of single-syllable words comprising high-frequency consonants and short vowel sounds (such as “sit”) and words in monosyllabic languages such as Chinese.
When the hearing-impaired listener communicates with others on a network telephone, a problem is that some Internet phones remove frequencies above 4,000 Hz.
Thus hearing-impaired listeners are in need of help in this regard.